Method of fabricating an alloy film on a face of a heat exchanger for an integrated circuit

ABSTRACT

An alloy film is fabricated, on the face of a heat exchanger for an integrated circuit, by a process that dispenses various liquids onto the heat exchanger&#39;s face. To prevent those liquids from falling off of the heat exchanger&#39;s face onto other components which hold the heat exchanger on a frame, the process begins by combining the heat exchanger into an assembly that includes a retainer and a compliant member. The retainer catches any liquids that fall off the heat exchanger&#39;s face, and the compliant member forms a seal between the heat exchanger and the retainer which prevents the liquids from leaking onto the other components.

RELATED CASE

[0001] The present invention, as identified by the above title and docket number, is related to another invention which is identified as follows: “MECHANICAL ASSEMBLY FOR FABRICATING AN ALLOY FILM ON A FACE OF A HEAT EXCHANGER FOR AN INTEGRATED CIRCUIT” having docket number 550,635 and U.S. Ser. No. ______. Patent Applications on both of these inventions were filed concurrently on Jul. ______, 2001, and they have one common Detailed Description.

BACKGROUND OF THE INVENTION

[0002] This invention relates to heat exchangers which regulate the temperature of an integrated circuit via thermal conduction by pressing against the integrated circuit. More particularly, this invention relates to methods and apparatus for use in fabricating a particular type of the above heat exchanger which has a face with an alloy film that presses against the integrated circuit.

[0003] In the prior art, U.S. Pat. No. 6,243,944 (hereafter patent '944) describes an array of several heat exchangers that are held by a frame in alignment with a corresponding array of integrated circuits on a printed circuit board, and each heat exchanger has a face with an alloy film that presses against a respective one of the integrated circuits. See, for example, FIG. 1 in patent '944 wherein each item 23 is one integrated circuit, and each item 15 is one heat exchanger. See also FIG. 6 in patent '944 wherein item 15 a is the face of one heat exchanger that presses against an integrated circuit, and item 15 b is an alloy film on the face 15 a.

[0004] By providing the alloy film 15 b on face 15 a of the heat exchanger, the thermal resistance between that face and the integrated circuit is greatly decreased. The alloy film affects the thermal resistance because the face of the heat exchanger, and the surface of the integrated circuit which that face presses against, are not perfectly smooth; and consequently, an irregular shaped microscopic gap exists between the face of the heat exchanger and the integrated circuit. But, when the alloy film on the face of the heat exchanger is melted, the alloy substantially fills the gap; and that causes the thermal resistance to decrease. This is shown in FIGS. 7 and 8 of patent '944.

[0005] The above concept for reducing thermal resistance applies to heat exchangers which have a wide variety of shapes and sizes, and which are held in an array by a wide variety of frames. For example, see U.S. Pat. No. 6,179,047 (hereafter patent '047) wherein FIG. 1 shows a frame 10 that holds multiple heat exchangers 20 in an array, and each heat exchanger has a face 21 on which an alloy film can be provided. See also, FIG. 10 of patent '047 which shows another heat exchanger 90 that can be held in an array by the frame 10, and this heat exchanger 90 has a face 91 on which an alloy film can be provided.

[0006] However, one problem with the above concept for reducing thermal resistance is how to refurbish the alloy film on the face of the heat exchangers after they have made contact with multiple integrated circuits. This refurbishment is occasionally needed when an array of heat exchangers are held by a frame and are used in equipment which tests many integrated circuits in a sequential fashion. There, when the test on one array of integrated circuits is complete, the heat exchangers are moved to another array of integrated circuits. After about one-thousand to three-thousand arrays of the integrated circuits have been tested, the alloy film on the face of the heat exchangers needs to be refurbished because the alloy film oxidizes and that changes its thermal characteristics.

[0007] If the alloy film is refurbished on the face of the heat exchangers while they are held by the frame, then various components which couple the heat exchanger to the frame can become contaminated by various fluids used in the refurbishment process. For example, FIG. 2 of patent '944 shows that to fabricate the alloy film, a flux must first be spread on the face of the heat exchanger. This flux promotes metallurgical bonding between the face of the heat exchanger and the metal alloy which is subsequently applied as shown in FIGS. 3 and 4. However, if a portion of the flux drips off the face of the heat exchanger, that flux could corrode other components such as the coil springs 20 in FIG. 1 of patent '944, the leaf springs 30 a-30 d in FIG. 1 of patent '047, and the leaf spring 80 in FIG. 10 of patent '047.

[0008] Alternatively, all of the heat exchangers can be removed from the frame before the alloy film is refurbished; and then all of the heat exchangers can be re-attached to the frame. However, the removing step and re-attaching step are time-consuming; and that adds to the cost of the refurbished process.

[0009] Also, another problem with the above concept for reducing thermal resistance is how to fabricate the alloy film such that it has a thickness which lies within a narrow preferred range. If the alloy film is too thin, then the irregular-shaped microscopic gap between the integrated circuit and the face of the heat exchanger will not be filled with alloy; and, that will increase the thermal resistance. Conversely, if the alloy film is too thick, then a portion of the alloy could get squeezed off of the heat exchange when the face of the heat exchanger is pressed against the integrated circuit; and that could cause a short-circuit in the test equipment. One preferred range for the thickness of the alloy where it is neither too thick or too thin is 75 μm-100 μm.

[0010] In FIG. 3 of patent '044, the thickness of the alloy film is controlled by placing a solid piece of alloy, of predetermined size, on the face of the heat exchanger; melting that alloy; and spreading the melted alloy to form the film. However, the alloy in FIG. 3 of patent '044 will form a film on the heat exchanger at all locations which are coated with flux. Thus, if some of the flux in FIG. 2 of patent '044 drips off of the face onto an adjacent region on the side of the heat exchanger, then that region will also be coated with the alloy film. Consequently, the thickness of the alloy film on the face of the heat exchanger will not be in the predetermined range.

[0011] Accordingly, a primary object of the present invention is to provide a method and apparatus for solving the above problems.

BRIEF SUMMARY OF THE INVENTION

[0012] The present invention, as claimed herein, is a method of fabricating an alloy film on a face of a heat exchanger for an integrated circuit. This method begins with the step of assembling the combination of -1) a retainer for liquid which has a bottom with an opening into which the heat exchanger extends such that the retainer surrounds the heat exchanger's face; and, 2) a compliant member, in the opening of the bottom of the retainer around the heat exchanger, which forms a seal between the heat exchanger and the retainer. Thereafter, a dispensing step is performed wherein various liquids (such as a liquid flux, liquid alloy, and water) are put on the heat exchanger's face in a sequence. During this dispensing step, at last a portion of the liquids fall of the heat exchanger's face into the retainer; and those liquids are removed from the retainer, by suction, for example. Then, after the alloy film is formed from the dispensed liquid, the empty retainer and the compliant member are moved to another heat exchanger on the frame and the above steps are repeated.

[0013] Throughout the above process, the compliant member prevents the liquids that fall into the retainer from leaking out of the retainer onto any other components which hold the heat exchanger on a frame. Also in one embodiment, the assembling step forms the seal around the heat exchanger adjacent to the heat exchanger's face; and that enables the alloy film to be fabricated with a precisely controlled thickness on the heat exchanger's face because no liquid flux or liquid alloy can inadvertently drip onto any region of the heat exchanger that is adjacent to the face.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is an exploded view of a mechanical assembly for fabricating an alloy film, in accordance with the present invention, on a face of a heat exchanger for an integrated circuit.

[0015]FIG. 2 is a top view of the mechanical assembly of FIG. 1.

[0016]FIG. 3 is a sectional view of the mechanical assembly in FIGS. 1 and 2, taken along line A in FIG. 2.

[0017]FIG. 4A lists the steps of a process which fabricates an alloy film, in accordance with the present invention, on the face of the heat exchanger that is in the assembly of FIGS. 1-3.

[0018]FIG. 4B lists the steps of a process which precedes the process of FIG. 4A to refurbish an alloy film on the face of the heat exchanger that is in the assembly of FIGS. 1-3.

[0019] FIGS. 5-12 each show one respective modification to the assembly of FIGS. 1-3.

DETAILED DESCRIPTION

[0020] Referring now to FIGS. 1, 2 and 3, a novel mechanical assembly, which is one preferred embodiment of the present invention, will be described in detail. Later, in conjunction with FIGS. 4A and 4B, a novel process will be described in detail which uses the above mechanical assembly in accordance with the present invention to fabricate an alloy film on the face of a heat exchanger for an integrated circuit chip.

[0021] In FIG. 1, component 11 is a heat exchanger which has a face 11 a for pressing against an integrated circuit chip. This face 11 a is on a pedestal 11 b which extends from a hollow body 11 c. The hollow body 11 c has an input port 11 d and an output port 11 e so that a fluid can be forced thru the hollow body when the face 11 a is pressing against the integrated circuit chip. This heat exchanger 11 exists in the prior art, and it is shown in FIG. 10 of patent '047 (as cited in the BACKGROUND).

[0022] Also in FIG. 1, component 12 is a retainer for various liquids that are used to fabricate the alloy film on face 11 a of the heat exchanger 11. This retainer 12 has a bottom 12 a with an opening 12 b; and, the pedestal 11 b on the heat exchanger 11 extends into the opening 12 b. In that position, the heat exchanger face 11 a is surrounded by a sidewall 12 c of the retainer 12. The sidewall 12 c also has three hollow passageways 12 d, 12 e and 12 f; and their function will be described later in conjunction with the process of FIGS. 4A and 4B.

[0023] Further in FIG. 1, component 13 is a compliant member which forms a seal between the heat exchanger 11 and the retainer 12. Due to that seal, the retainer 12 will hold various liquids that are used in the process of FIGS. 4A and 4B to fabricate the alloy film on face 11 a of the heat exchanger 11. That is important because it enables the alloy film to be fabricated on the face 11 a while the heat exchanger 11 is held by a frame, without contaminating any parts that couple the heat exchanger to the frame.

[0024] A prior art example of how the heat exchanger 11 can be held by a frame is shown in FIG. 10 of patent '047. There, the heat exchanger is identified by reference numeral 90; the frame is identified by reference numeral 70; and the heat exchanger is coupled to the frame by a pair of stops 100 and a spring 80. Also, several copies of the FIG. 10 structure can be attached, by screws, in an array onto a larger frame, such as the frame 10 or the frame 10′ that are respectively shown in FIG. 1 and FIG. 9 of patent 047.

[0025] In FIG. 1 of the present invention, the compliant member 13 consists of a thin stretchy membrane 13 a and a ring-shaped attaching part 13 b. This membrane 13 a extends across the opening 12 b on the bottom of the retainer 12, and the ring-shaped attaching part 13 b fits snugly into the opening 12 b. Consequently, the ring-shaped attaching part 13 b holds the membrane 13 a on the retainer 12 by squeezing the perimeter of the membrane 13 a against the retainer 12 around the opening 12 b.

[0026] Located in the center of the membrane 13 a is a hole 13 c; and it has a perimeter which stretches around the face 11 a of the heat exchanger 11. Due to this stretchy structure, a seal is formed which exposes the heat exchanger's face 11 a and exposes no portion of the pedestal 11 b which lies adjacent to the face 11 a. Consequently, no liquids which are used to fabricate the alloy film on the face 11 a will spill onto an adjacent portion of the pedestal 11 b. That is important because it enables the alloy film to be fabricated with a preferred thickness and small tolerances.

[0027] When the components 11, 12 and 13 of FIG. 1 are coupled together, they form the assembly that is shown in FIGS. 2 and 3. In that assembly, all of the components and their physical features are identified by the same reference numerals that they have in FIG. 1.

[0028] Also in the assembly of FIGS. 2 and 3, reference numeral 21 identifies the seal which the thin stretchy membrane 13 a makes with the heat exchanger 11 around the face 11 a. Similarly in FIG. 3, reference numeral 22 identifies the seal which the thin stretchy membrane 13 a and the ring-shaped attaching part 13 b make with the heat exchanger 11 around the opening in the retainer bottom 12 a.

[0029] One feature of the assembly in FIGS. 2 and 3 is that the seals 21 and 22 are easily made and are easily undone. To make the seal 21, the pedestal 11 b is simply pushed thru the hole 13 c in the stretchy membrane 13 a. To make the seal 22, the perimeter of the stretchy membrane 13 a is simply squeezed between the retainer bottom 12 a and the ring-shaped part 13 b.

[0030] Consequently, when a plurality of the heat exchangers 11 are held in an array by a frame, then the assembly of FIGS. 2 and 3 can be easily formed with each heat exchanger in a sequential fashion. This is achieved simply by moving the retainer 12 and the compliant member 13 from one heat exchanger to another. Each time the assembly of FIGS. 2 and 3 is formed with one particular heat exchanger, the process steps of FIGS. 4A and 4B can be performed to form an alloy film on the face 11 a of that heat exchanger.

[0031] Another feature of the assembly in FIGS. 2 and 3 is that the seal 21 will form around the heat exchanger face 11 a, even when the face 11 a is changed in size and shape over a wide range. This feature occurs because the membrane 13 a will stretch to accommodate various sizes and shapes for the face 11 a and the pedestal 11 b. Consequently, the assembly of FIGS. 2 and 3 can be formed with several different heat exchangers, and a separate membrane 13 a does not need to be tailored for each heat exchanger.

[0032] Now, with reference to FIG. 4A, one preferred process will be described which uses the mechanical assembly of FIGS. 1, 2 and 3 to fabricate an alloy film on the heat exchanger's face 11 a. This process is performed by a sequence of steps which are listed as steps S1-S11 in FIG. 4A. Each of the steps S1-S11 can be performed either manually by a workman or automatically by a machine.

[0033] Associated with each of the steps S1-S11 is a “TIME” parameter, a “PASSAGEWAY” parameter, and a “SPILLAGE” parameter. The “TIME” parameter specifies how long, in seconds, the step is performed. The “PASSAGEWAY” parameter identifies each passageway 12 d, 12 e, or 12 f that is used to pass a fluid while the step is performed. And, the “SPILLAGE” parameter indicates whether or not any fluid spills from the heat exchanger's face 11 a into the retainer 12 while the step is performed.

[0034] The purpose of the passageway 12 f is to put water into the retainer 12 to wash the heat exchanger face 11 a. The purpose of the passageway 12 e is to remove any fluid, and any debris in the fluid, from the retainer 12 but only up to the level of the heat exchanger's face 11 a. The purpose of the passageway 12 d is to remove any fluid, and any debris in the fluid, in their entirety, from the retainer 12.

[0035] Removal of fluid and debris thru the passageways 12 d and 12 e occurs by applying a vacuum to those passageways. Fluid and debris is removed in its entirety thru the passageway 12 d because the elastic membrane 13 a slopes down and away from the heat exchanger's face 11 a, and the passageway 12 d starts at the lowest point inside the retainer 12. By comparison, the passageway 12 e starts at a point within the retainer 12 that is level with the heat exchanger's face 11 a.

[0036] In step S1 of FIG. 4A, the assembly of FIG. 3 is formed. To do that, the stretchy membrane 13 a is first placed on the heat exchanger pedestal 11 b such that the seal 21 is formed around face 11 a. Next, the perimeter of the stretchy membrane 13 a is draped over the ring-shaped attaching part 13 b. Then, the retainer 12 is pushed onto the ring-shaped attaching part 13 b such that the perimeter of the stretchy membrane 13 a is squeezed between the ring-shaped part 13 b and the retainer 12. This step S1 takes only about thirty seconds to complete.

[0037] In step S2, a liquid flux is dispensed on the heat exchanger's face 11 a. This flux is any chemical that will promote metallurgical bonding between the heat exchanger's face 11 a and the alloy film which is to be fabricated on that face. For example, once such flux is a mixture of 70%-80% alcohol, 15%-25% carboxylic acid, and 10%-20% amine hydrochloride.

[0038] In step S3, a solid piece of alloy, of a predetermined size, is picked-up and placed on the heat exchanger's face 11 a. The size of this solid piece of alloy is selected such that after the alloy is melted and spread uniformly across the heat exchanger's face 11 a, it will have a preferred thickness. One such thickness is 75 μm-100 μm.

[0039] In step S4, the alloy from step S3 is melted and spread across the heat exchanger's face 11. This can be done, for example, by using a tool with a hot tip that melts the alloy. With this step, the main object is simply to cover the entire face 11 a with alloy, and the thickness of the alloy need not be uniform.

[0040] In step S5, additional liquid flux is dispensed onto the alloy on the heat exchanger's face 11 a. Preferably this flux has a diluted concentration. If the flux is not diluted, then the alloy layer from step S4 might de-wet from face 11 a, and the case which the alloy spreads uniformly in step S6 will decrease.

[0041] In step S6, the alloy film that was formed in step S4 is spread into a smooth and uniformly thick film. Here again, the spreading can be done by using a tool with a hot tip that melts the alloy.

[0042] In step S7, water is sent thru the passageway 12 f into the retainer 12. This water flows until the water level in the retainer 12 is approximately one-eighth inch above the heat exchanger's face 11 a. The total mount of water which is sent into the retainer 12 is controlled by the flow rate of the water and the time duration of step S7. By this step, a preliminary cleaning of the face 11 a occurs.

[0043] In step S8, any bumps or similar imperfections in the alloy film on face 11 a are made smooth. This is achieved by touching the bumps, and/or smoothing the bumps, with the hot tip of a tool. During this step, the water in retainer 12 remains at the level which is set in step S7.

[0044] In step S9, only a pause occurs. This ensures that any remaining flux and flux residue dissolves with the water that was put into the retainer 12 in step S7. Also during this pause, any small bumps or dimples in the alloy film can be touched-up with the hot tip of a tool before steps S10 and S11 are performed.

[0045] In step S10, the alloy film on the heat exchanger's face 11 a is thoroughly washed and rinsed. This is achieved by sending water thru the passageway 12 f into the retainer 12, while concurrently removing that water together with any residue debris thru the passageway 12 e.

[0046] Lastly, in step S11, the retainer 12 is completely depleted of any water and residue debris, and the retainer 12 along with the heat exchanger's face 11 a is dried. This is achieved by applying a vacuum to the passageway 12 d.

[0047] Inspection of the “SPILLAGE” parameters in FIG. 4A shows that during steps S2, 5, S7, and S10-S11, either flux or water can spill off of the heat exchanger's face 11 a. However, due to the operation of the retainer 12 and the compliant member 13, none of that spillage will contaminate or otherwise damage any parts that couple the heat exchanger 11 to the frame. Prior art examples of these parts and the frame are shown in the previously cited FIGS. 1, 9 and 10 of patent '047.

[0048] Also, due to the seal 21 that is formed by the compliant member 13, only the heat exchanger's face 11 a and no adjacent portion of the heat exchanger's pedestal 11 b is exposed to the flux and the alloy and the water that is used by the process of FIG. 4A. Further, by carefully spreading and smoothing the alloy in steps S4, S6 and S8, all of the alloy which is dispensed in step S3 will remain on the heat exchanger's face 11 a. Due to these two points, the alloy film which is fabricated on the heat exchanger's face has a precisely controlled thickness.

[0049] After the alloy film has been fabricated on the heat exchanger's face 11 a by the process of FIG. 4A, the heat exchanger 11 is ready to be used in test equipment which tests integrated circuit chips in a sequential fashion. Each time one integrated circuit chip is tested, the heat exchanger's face and the integrated circuit chip are pressed together, and the alloy film melts to thereby fill microscopic gaps between the heat exchanger's face 11 a and the integrated circuit chip. However, when the alloy film is used in such equipment, the alloy film slowly oxidizes; and, after about one-thousand to three thousand cycles, the alloy film on the heat exchanger's face 11 a needs to be refurbished.

[0050] This refurbishment is done, in accordance with the present invention, by performing steps S21-S31 of FIG. 4B, followed by steps S2-S11 of FIG. 4A. The FIG. 4B process begins with step S21 wherein the assembly of FIG. 3 is formed, as was previously described in conjunction with step S1.

[0051] In step S22, the alloy layer which was previously put on the heat exchanger's face 11 a and which is now at least partially oxidized, is melted and removed. This removal is achieved by dispensing water on the heat exchanger's face while concurrently using an aspirator to suck a mixture of the melted alloy and the water from the heat exchanger's face. Any excess mixture is removed from the retainer 12 thru the passageway 12 d.

[0052] In steps S23 and S24, various inter-metallic compounds and oxidized alloy and residue, which forms on the heat exchanger's face 11 a, are removed. This is achieved by first scrubbing the heat exchanger's face with water, in step S23. Then in step S24, a mixture of the scrubbed-off inter-metallics and oxidized alloy and residue and water is removed with an aspirator. Again, any excess mixture is removed from the retainer 12 thru the passageway 12 d.

[0053] In steps S25-S28, any oxidized metal in the heat exchanger's face 11 a is removed, and then the heat exchanger's face 11 a is covered with a thin coat of the alloy. This is achieved by first performing step S25 wherein flux is dispensed on the heat exchanger's face 11 a. Next in step S26, a small amount of alloy is put on the heat exchanger's face and melted. Then in step S27, the melted alloy is spread into a non-uniform thin coat across the heat exchanger's face 11 a. Lastly, in step S28, water is dispensed on the alloy coating; and a mixture of that water and alloy and any residual materials on the alloy coating are removed with an aspirator. This leaves a thin alloy film on the heat exchanger's face 11 a which is only about one-tenth as thick as the film which is formed by the process of FIG. 4A.

[0054] In steps S29-S31, the thin coat of alloy on the heat exchanger's face 11 a is completely cleaned and dried. Step S29 is performed just like step S7 in FIG. 4A; step S30 is performed just like step S10 in FIG. 4A; an d step S31 is performed just like step S11 in FIG. 4A.

[0055] Inspection of the “SPILLAGE” parameters in FIG. 4B shows that during steps S22-S25 and S27-S31, either flux or alloy or water can spill off of the heat exchanger's face 11 a. However, due to the operation of the retainer 12 and the compliant member 13, none of that spillage will contaminate or otherwise damage any parts that couple the heat exchanger 11 to the frame.

[0056] One preferred embodiment of a novel mechanical assembly, which is structured in accordance with the present invention, has now been described in detail. Also, one preferred process which fabricates and refurbishes an alloy film on the face of the heat exchanger, in accordance with the present invention, has now been described in detail. However, various modifications can be made to the above details without departing from the scope of the invention; and, some examples of such modifications will now be described in conjunction with FIGS. 5-12.

[0057] In FIG. 5, reference numeral 52 identifies a retainer which is a modified version of the retainer 12 in FIGS. 1-3. Here, the only modification is that the bottom 52 a of the retainer does not extend inward past the sidewall 52 c of the retainer, as it does in FIGS. 1-3. Also in FIG. 5, reference numeral 53 identifies a compliant member which is a modified version of the compliant member 13 in FIGS. 1-3. This compliant member 53 includes the thin stretchy membrane 13 a with its hole 13 c as shown in FIGS. 1-3. Also, the compliant member 53 includes a ring-shaped attaching part 53 b which squeezes the perimeter of the stretchy membrane 13 a against the exterior surface of the retainer's sidewall 52 c.

[0058] In FIG. 6, reference numeral 12 identifies the retainer 12 from FIGS. 1-3; and, reference numeral 63 identifies a compliant member which is a modified version of the compliant member 13 in FIGS. 1-3. This compliant member 63 includes the thin stretchy membrane 13 a with its hole 13 c from FIGS. 1-3. Also, the compliant member 63 includes a ring-shaped attaching part 63 b which squeezes the perimeter of the stretchy membrane 13 a against the interior surface of the retainer's sidewall 12 c.

[0059] In FIG. 7, reference numeral 12 identifies the retainer 12 from FIGS. 1-3; and, reference numeral 73 identifies a compliant member which is a modified version of the compliant member 13 in FIGS. 1-3. This compliant member 73 includes a rigid ring-shaped part 73 a which has an inner sidewall that holds a seal ring 73 b, and which has an outer sidewall that holds a seal ring 73 c. The seal ring 73 b has a shape which surrounds the pedestal 11 b of the heat exchanger 11 in FIG. 1 and forms a seal adjacent to the heat exchanger's face 11 a. The seal ring 73 c has a shape which fits into the retainer 12 and forms a seal with the interior of the retainer's sidewall 12 c.

[0060] In FIG. 8, reference numeral 82 identifies a retainer which is a modified version of the retainer 12 in FIGS. 1-3; and reference numeral 73 identifies the compliant member 73 from FIG. 7. The modification which is in the retainer 82 is that the retainer's bottom 82 a has a notch into which the compliant member 73 snugly fits as shown; and the seal ring 73 c forms a seal in that notch.

[0061] In FIG. 9, an assembly is shown which is similar to the assembly of FIGS. 1-3 but in which the ring-shaped attachment part 13 b is eliminated. To accomplish that, the assembly of FIG. 9 includes a heat exchanger 91 and a retainer 92 that has a bottom surface 92 a with an opening into which the heat exchanger snugly fits. The FIG. 9 assembly also includes the thin stretchy membrane 13 a of FIGS. 1-3, and that membrane is squeezed against the retainer 92 by the heat exchanger 91, as shown, to form the seal 22. The thin stretchy membrane 13 a also forms the other seal 21 around the heat exchanger's face 91 a, just like it does in FIGS. 1-3.

[0062] In FIG. 10, a modification is shown to the previously described thin stretchy membrane 13 a of FIG. 1. Here, the modification is that a layer of sticky material 13 d is attached to a portion of the membrane 13 a which is adjacent to the hole 13 c. When this modification is incorporated into the assemblies of FIGS. 1-3, 5, 6 and 9, the sticky material 13 d contacts the pedestal 11 b of the heat exchanger 11 around the heat exchanger's face 11 a, and that enhances the seal 21. One specific example of a suitably sticky material 13 d is double-sided silicone tape.

[0063] In FIG. 11, an assembly is shown which is similar to the assembly of FIG. 8 but in which the ring-shaped part 73 a and the seal ring 73 c are eliminated. To accomplish that, the assembly of FIG. 11 includes a retainer 112 that has a bottom 112 a with an opening that is slightly larger than the face 11 a of the heat exchanger 11 in FIG. 1. A seal ring 112 b is held by the bottom of the retainer 112, and that seal ring presses against the pedestal 11 b of the heat exchanger 11 of FIG. 1 to thereby form the seal 21.

[0064] In FIG. 12, a modification is shown to the heat exchanger 11 of FIG. 1. Here, the modification is that the pedestal of the heat exchanger 11 is coated with a material 11 f which will not wet the alloy that is fabricated on the heat exchanger's face 11 a by the process of FIG. 4A. Examples of the material 11 f are: 1) a Teflon coating, 2) a silicone coating, and 3) Teflon tape with a silicone adhesive. With this modification, the seal 21, as shown in FIG. 3, can occur anywhere on the heat exchanger's pedestal and need not be made adjacent to the heat exchanger's face 11 a.

[0065] All of the above assemblies of FIGS. 5-12 can be used in the process of FIGS. 4A and 4B. Also, various steps in the process of FIGS. 4A and 4B can be modified. For example, the liquids that are used in process of FIGS. 4A and 4B can be drained by gravity from the retainer 12, rather than be sucked by a vacuum thru the passageway 12 d and 12 c. To implement this modification, the passageways 12 d and 12 e need to extend from the inside of the retainer 12 in a downward direction to the outside of the retainer 12. Tubes can connect to those passageways and drain the fluid away from the frame on which the heat exchangers are held.

[0066] Accordingly, it is to be understood that the scope of the present invention is not limited to details of any one particular assembly or process that is shown in the FIGS. 1-12, but is defined by the appended claims. 

What is claimed is:
 1. A method of fabricating an alloy film on a face of a heat exchanger for contacting an integrated circuit; said method including the steps of: assembling the combination of 1) a retainer for a liquid which has a bottom with an opening into which said heat exchanger extends such that said retainer surrounds said heat exchanger's face; and, 2) a compliant member, in said opening around said heat exchanger, which forms a seal for said liquid between said heat exchanger and said retainer; dispensing said liquid onto said face of said heat exchanger such that at least a portion of said liquid falls from said face into said retainer; and, removing said portion of said liquid from said retainer.
 2. A method according to claim 1 wherein said heat exchanger is held on a frame by additional components, and said assembling step forms said seal such that said liquid cannot leak from said retainer onto said additional components.
 3. A method according to claim 2 wherein said assembling step forms said seal completely around, and adjacent to, said heat exchanger's face.
 4. A method according to claim 2 wherein said heat exchanger has a coating, adjacent to said heat exchanger's face, which said alloy does not wet; and said assembling step forms said seal completely around said heat exchanger's face, but spaced therefrom, on said coating.
 5. A method according to claim 2 wherein said dispensing step includes the substep of applying a liquid flux to said heat exchanger's face which promotes metallurgical bonding between said face and said alloy.
 6. A method according to claim 2 wherein said dispensing step includes the substep of washing said heat exchanger's face with water.
 7. A method according to claim 2 wherein said dispensing step includes the substep of spreading said alloy in a liquid state into a film across said heat exchanger's face.
 8. A method according to claim 2 wherein said dispensing step includes the substep of scrubbing said heat exchanger's face with said liquid.
 9. A method according to claim 2 wherein said dispensing step is performed in a series of separate time intervals during which at least two different liquid materials are dispensed on said heat exchanger's face.
 10. A method according to claim 2 wherein said removing step is performed by aspirating said portion of said liquid from said retainer.
 11. A method according to claim 2 wherein said removing step is performed by draining said portion of said liquid from said retainer.
 12. A method according to claim 2 wherein said assembling step includes the substeps of -a) providing a stretchy membrane within said compliant member which has a hole with a stretchy perimeter; and b) stretching the perimeter of said hole in said stretchy membrane around said heat exchanger's face.
 13. A method according to claim 2 wherein said assembling step includes the substeps of -a) providing a seal ring within said compliant member; and b) pushing said seal ring onto said heat exchanger around said heat exchanger's face.
 14. A method according to claim 2 wherein said assembling step, dispensing step, and removing step are repeated in a sequence multiple times, and where between each repetition, said retainer and said complaint member are moved from one heat exchanger to another heat exchanger on said frame. 